1645 in Denmark

Events from the year 1645 in Denmark.

Incumbents

Monarch — Christian IV{{cite web |title=Christian IV {{!}} Scandinavian king |url=https://www.britannica.com/biography/Christian-IV |website=Encyclopedia Britannica |access-date=19 November 2019 |language=en}}
Steward of the Realm — Corfitz Ulfeldt

3 March — Simon Paulli gives his first public lecture in the new Domus Anatomica in Copenhagen.{{cite web|url=http://www.kobenhavnshistorie.dk/bog/kko/d/kko_d-9.html|title=Domus Anatomica|language=da|publisher=Selskabet for Københavns Historie|access-date=2012-04-20|archive-url=https://web.archive.org/web/20120324015513/http://www.kobenhavnshistorie.dk/bog/kko/d/kko_d-9.html|archive-date=2012-03-24|url-status=dead}}
25 May {{ndash}} {{HDMS|Stora Sofia}} sinks near Buskär outside the harbour of Gothenburg.
13 August — The Second Treaty of Brömsebro is signed, putting an end to the Torstenson War. The island Øsel is ceded to Sweden.

Stephanius publishes Saxonis Grammatici Historiæ Danicæ Libri XVI, a Latin edition of Saxo Grammaticus's Gesta Danorum.

File:Wuchters, Abraham - Ulrik Christian Gyldenløve (KMS617).jpg|Abraham Wuchters' portrait of Ulrik Christian Gyldenløve.